Nitrogen (N) is an essential nutrient for forage grasses and it is often associated with the intensification of forage-based animal production systems. Biological nitrogen fixation and the use of of N-fixing bacteria is a low-cost and sustainable option for supplying plants with N, against a scenario of increased production costs and increased environmental pressures. However, there are no studies with crop models to simulate these systems with the contribution of bacterial inoculation as a source of N supply to the forage. The objective of the present study is to parameterize and test the efficiency of the APSIM-Tropical Pasture and CROPGRO-Perennial Forage models to simulate the productivity of the Ipyporã brachiariagrass [Brachiaria spp. (syn. Urochloa spp.) cv. BRS331 Ipyporã] under the effect of bacterial inoculation. For this, data from an experiment performed at Embrapa Agrossilvipastoril in Sinop - MT, in a randomized complete block design, with four treatments applied in pastures of Ipyporã brachiariagrass, with three replicates: (1) without nitrogen fertilization (control); 2. fertilized with 80 kg N ha-1 y-1; (3) inoculation with Azospirillum brasilense; (4) fertilized with 80 kg N ha-1 y-1 + inoculant. Afterwards, calibrations of the models will be carried out and a comparative analysis between the models to simulate the pasture productivity for all the scenarios. The expected results are to construct parameterizations of the models with good efficiency in estimating the productivity of a hybrid of Brachiaria in monoculture and fertilized, managed under rotational defoliation and to estimate the effect of the bacterial inoculation in these systems.
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